Dimensional Parasitics Absorption in Capacitively-Isolated Ćuk Converter for Medium-Voltage High Step-Down Converters

The demand for medium-voltage direct current (MVdc) power distribution in land-constrained residential areas has highlighted the need for compact power processors and architectures. High-density power distribution requires co-packaging of power passive components and switches to enhance power densities while addressing insulation and thermal management for medium-voltage (MV) systems. However, such designs inherently introduce parasitics within the converter. This work focuses on absorbing these parasitics as manifestations of non-linear insulation and coaxial structural constraints. The capacitively-isolated Ćuk converter (CIĆC) is proposed as a high step-down solution for modular converters. The CIĆC mitigates parasitics, enabling integration into input-series output-parallel (ISOP) architectures, such as solid-state transformers (SSTs). By using the dielectric for both insulation and energy transfer, the CIĆC eliminates transformer-based cells in SSTs. Additionally, this work achieves a significant reduction in the blocking capacitor size required for zero-voltage switching (ZVS). The proposed topology is validated using a custom-packaged 2 kV-to-400 V, 50 kW coaxial modular converter operating at 100 kHz, achieving a power density of 8 MW/m³. These results demonstrate the CIĆC’s potential to address the challenges of high-density, modular MV power conversion.